Development of excited-state bond homolysis as a key step for Ni catalysis

能够合成复杂分子支架的键结构方法是人们感兴趣的关键 制药业。为此，镍催化已成为构筑C(Sp2)-的一种通用工具。 C(Sp2)、C(Sp3)-C(Sp2)和C(Sp3)-C(Sp3)键。倪成功地完成了这些转变在于 镍参与单电子和双电子过程的能力--通过0，I，II和III氧化循环 各州。因此，除了规范的双电子过程(迁移插入、b-氢化物消除、 等)中，经常会遇到抽象、自由基捕获和电子转移等基本步骤 镍催化作用。镍催化也成为光化学在过渡中整合的卓有成效的平台- 金属催化。最近，我们的研究小组发现，在光照射下，芳基镍(BPY)络合物可以进行 激发态键均裂生成C(Sp2)自由基。这些初步的化学计量研究表明 光能可以选择性地导向镍，从原料化学品中产生高活性的中间体 先驱物。我们建议将光消除NiI作为一种通用步骤应用于镍催化。 交叉偶联反应的传统发展侧重于从序列中获得新的结果 已知的基本过程。这一建议是独一无二的，因为它是基于一种新的 镍催化的基本步骤。我们的努力将利用单电子和双电子之间的相互作用 镍可利用的工艺，以解决目前文献中选择性和反应性方面的限制。这个 这里描述的研究将包括三个目标：(1)开发改进量子的方法 激发态镍键均裂过程的产率，(2)探索和扩展有机自由基中心的范围 (3)将光消除作为镍催化的基本步骤。三个都是 Aspects将同时进行探索，并共同代表第一排领域令人兴奋的新方向 过渡金属催化。

Methods for bond construction enabling the synthesis of complex molecular scaffold are of key interest to the pharmaceutical industry. To this end, Ni catalysis has emerged as a versatile tool for the construction of C(sp2)– C(sp2), C(sp3)–C(sp2), and C(sp3)–C(sp3) bonds. The success of Ni in accomplishing these transformations lies in the ability of Ni to engage in both single- and two-electron processes – cycling through 0, I, II, and III oxidation states. As a result, in addition to canonical two-electron processes (migratory insertion, b-hydride elimination, etc.), fundamental steps such as abstractions, radical captures, and electron transfers are often encountered in Ni catalysis. Ni catalysis has also served as a fruitful platform for the integration of photochemistry in transition- metal catalysis. Recently, our group found that upon irradiation with light, aryl NiII(bpy) complexes can undergo excited-state bond homolysis to generate C(sp2) radicals. These initial stoichiometric studies demonstrate that light energy can be selectively directed to Ni to generate highly reactive intermediates from feedstock chemical precursors. We propose leveraging photoelimination from NiII as a general step to be employed in Ni catalysis. Traditional development of cross-coupling reactions focuses around achieving new outcomes from sequences of known fundamental processes. This proposal is unique as it is based on the development of a new fundamental step for Ni catalysis. Our efforts will capitalize on the interplay between single- and two- electron processes accessible to Ni to address limitations in selectivity and reactivity in the present literature. The research described herein will be comprised of three aims: (1) developing approaches for improving quantum yield of excited-state Ni bond homolysis processes, (2) explore and extend the scope of organic radical centers accessed by photoelimination, and (3) employing photoelimination as fundamental step in Ni catalysis. All three aspects will be explored concurrently and together represent an exciting new direction in the field of first-row transition metal catalysis.